[Influenza vaccination and hospitalization in high risk patients]

We aimed to analyze the degree of utilization of influenza vaccines in patients who are 65 years and older with decompensated chronic diseases during the 2006-07 influenza epidemic and to compare it with the 2000-01 epidemic. We also investigated the effectiveness of the influenza vaccination in the prevention of incomes for cardiopulmonary illness in this group.

Six hundred and forty two patients were studied; average (standard deviation) age was 74 (10) years, and 404 (63%) were males. Patients considered as cases had been admitted to hospital due to cardiopulmonary illness during the influenza season. Controls were patients attended at hospital but who had not been hospitalized during that period.

The population vaccination rate was 445 (68%). In the vaccination group, 275 (57%) people were 75 year old or more vs 77 (37%) patients in the non-vaccination group (p<0.001); 418 (94%) of the vaccination group had been vaccinated in previous years, vs 96 (46%) in the non-vaccination group (p<0.001). Cases were 337 (68%) vs 305 (31%) controls. Cases had major morbidity, previous hospitalization or pneumonia, as well as 2 or more risk factors -292 (85%) cases vs 225 (73%) controls (p<0.001)-. Factors mostly influencing the possibility of hospitalization were: influenza vaccination (odds ratio [OR]=0.59; 95% confidence interval [CI]: 0.41-0.86; p=0.006), chronic ischemic heart disease (OR=0.59; 95% CI, 0.40-0.88; p=0.009), high blood pressure (OR=1.60; 95% CI, 1.03-2.47), and previous hospitalization (OR=2.40; 95% CI, 1.64-3.49; p<0.001).

In high risk patients, the influenza vaccination rate was improved slightly in the last 6 years. Vaccination was associated with less hospitalization for heart and pulmonary diseases. These benefits of vaccination support future efforts to increase the rates of vaccination among elder patients with chronic diseases, especially if they have not been vaccinated in previous campaigns.